Device for the stereophonic recording of sound vibrations



Alig. 7, 1951 DE BOER ETAL 2,563,010

DEVICE FOR THE STEREOPHONIC RECORDING OF SOUND VIBRATIONS Filed Sept. 24, 1945 ATTORNEY Patented Aug. 7, I951 FOR THE STEREO PHONIC RECORD- ING OF SOUND VIBRATIONS Kornelis de Boer and Arend Thomas van Urk, v,Eindhoven, Netherlands, assignors to Hartford National Bank & Trust 00., Hartford, Conn, as

trustee Application September 24, 1945, Serial No. 618,334 In the Netherlands May 17,1943

' Section 1, Public Law 690, August s, 1946 Patent expires Mas 17, 1963 3 Claims. 1

Inthe stereophonic recording of sound vibrations by means of two microphones that are spaced apart from each other this distance, as is well known, must be different for different sound sources. In fact, in reproducing a whole orchestra this distance will have to be larger than in reproducing a single speaker, for instance, an actor, for as faithful as possible a reproduction.

In the case of two microphones being positioned independently from each other this involves little difficulties. Trouble is experienced, however, when making use of a so-called artificial head i. e. a preferably spherical body with two microphones provided on either side, which body constitutes an acoustic obstacle to sound vibrations. In this case several artificial heads having different diameters will be necessary, which is not only cumbersome, but also comparatively expensive.

In conjunction therewith it has already been proposed to equip such an artificial head with four microphones, two on either side, which are electrically intercoupled in such a manner that the apparent distance between the two microphone combinations is variable.

The present invention likewise concerns a device comprising an artificial head and has for its object to provide a solution which is as effective as the aforesaid method, but much more economical.

The device according to the invention is characterized in that the used artificial head constitutes an adjustable acoustic obstacle.

The advantage of a device according to the invention consists in that a minimum number of microphones, preferably two, is sufiicient and in that no additional electric circuit arrangements are necessary, so that the assembly will be much cheaper than the common devices.

According to one form of construction of the device the artificial head consists of two halves which by means of a pin in one half, which fits a hole in the other half, are free to turn with respect to one another, a microphone being secured to each half.

For a faithful reproduction, it is desirable that the two microphones should extend in a horizontal plane. This can, for instance, be achieved by making the artificial head rest in a base having a hollow, so that it can be given any desired position.

In order that the invention may be clearly understood and readily carried into effect, it will now be described more fully with reference to the accompanying drawin given by way of example.

Figure 1 represents a device according to the invention entirely ready for use.

Figure 2 representing the same device, whose three parts have been detached.

In the drawing the reference numbers I and 2 denote hemispheres having secured to them microphones 3 and 4. The assembly is footed on a base 5. In Figure 1 the artificial head is arranged in such a manner that by turning the parts I and 2 relatively to one another the distance between the two microphones is small, so that it may be used for reproducing a speaker. Moreover, a part of the artificial head is placed on the base in such a manner that the microphones extend in a horizontal plane.

Figure 2 shows that the hemisphere 2 is furnished with a pin 6 fitting an aperture 1 of the hemisphere I, so that the hemispheres are free to turn with respect to one another. The base 5 is furnished with an excavation 8 in which the lower sphere is seated. As a result thereof it can be achieved in all cases occurring in practice that the two microphones extend in a horizontal plane by turning the spheres in the base.

Of course, the invention is not limited to the aforesaid forms of construction, since the idea underlying the invention comprises any device in which the microphones on the artificial head are movable with respect to each other, to which end they may be so mounted as to be movable on the artificial head. Another possibility consists in a modification in shape or volume of the artificial head itself. Also in this case the artificial head need not be spherical, since it may be desirable to give it a different shape for the obtaimnent of definite eifects.

What we claim is:

1. A device for the stereophonic recording of sound vibrations, comprising a head member having a pair of portions, means for mounting one of said portions in rotatable relationship to said other of said portions, and microphones attached to each said portion and spaced apart with respect to each other, said member constituting an acoustical obstacle between said microphones, said microphones being adjustably positionable with respect to each other upon rotative motion of said portions relative to each other.

2. A device for the stereophonic recording of sound vibrations comprising two substantially hemispherical members, said members being rotatably joined together to form a substantially spherical head, and two microphones one secured to each said member and spaced apart, said head constituting an acoustical obstacle between said microphones, a, base member, and means on said base member for mounting one of said rotatable hemispherical members of said head for universal adjustment therewith, and means whereby said microphones are adjustably positionable with respect to each other in a desired plane upon rotation of one of said members relative to the other and movement of said one rotatable hemispherical member on said base.

3. A device for the stereophonic recording of sound vibrations, comprising two substantially 10 hemispherical members each having an axis of symmetry, each of said members being concentric and coaxially positioned to form a substantially spherical head, a pin coaxially positioned in said head, one of said members being adjustably rotatable about said pin with respect to the other member, two microphones one secured to each said member and being adjustably positionable with respect to each other upon rotation of one of said hemispherical members, said head constituting an acoustical obstacle between said microphones, and a base having a, spherically hollow portion to provide a rest for said head.

KORNELIS DE BOER.

AREND THOMAS VAN URK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 15 1,329,925 Perkins Feb. 3, 1920 1,855,146 Jones Apr. 19, 1932 1,855,149 Jones Apr. 19, 1932 2,414,695 Massa Jan. 21, 1947 

